python traverses the folder to find the file whose folder suffixes py

I graduated from college and wanted to see how many lines of code My college had written.

#coding=utf-8
import os
class Solution:
 def __init__(self):
  self.dirPath = []
 
 def numberOfCode(self,path):
  for dir in os.listdir(path):
   childDir = os.path.join(path,dir)
   if os.path.isdir(childDir):
    self.numberOfCode(childDir)
   else:
    if childDir[-2:] == "py":
     self.dirPath.append(childDir)
  return self.dirPath
 
 def setCode(self):
  with open("/home/code.py","ab+") as f:
   for file in self.dirPath:
    content = open(file,"r").read()
    f.write(content)
s = Solution()
s.numberOfCode("/home/py/")
s.setCode()